Neither the National Building Code of Canada (NBCC) , nor any provincial code, such as the British Columbia Building Code (BCBC) , currently provide “acceptable solutions” to permit the construction of tall wood buildings, that is buildings of 7 stories and above. British Columbia, however, was the first province in Canada to allow mid-rise (5/6 storey) wood construction and other provinces have since followed. As more mid-rise wood buildings are erected, their benefits are becoming apparent to the industry, and therefore they are gaining popularity and becoming more desirable.
Forest product research has now begun to shift towards more substantial buildings, particularly in terms of height. High-rise buildings, typically taller than 6 storeys, are currently required to achieve 2 h fire resistance ratings (FRR) for floors and other structural elements, and need to be of non-combustible construction, as per the “acceptable solutions” of Division B of the NBCC . In order for a tall wood building to be approved, it must follow an “alternative solution” approach, which requires demonstrating that the design provides an equivalent or greater level of safety as compared to an accepted solution using non-combustible construction. One method to achieve this level of safety is by ‘encapsulating’ the assembly to provide additional protection before wood elements become involved in the fire, as intended by the Code objectives and functional statements (i.e., prolong the time before the wood elements potentially start to char and their structural capacity is affected). It is also necessary to demonstrate that the assembly, in particular the interior finishes, conform to any necessary flame spread requirements.
The Technical Guide for the Design and Construction of Tall Wood Buildings in Canada  recommends designing a tall wood building so that it is code-conforming in all respects, except that it employs mass timber construction. The guide presents various encapsulation methods, from full encapsulation of all wood elements to partial protection of select elements. National Research Council Canada (NRC), FPInnovations, and the Canadian Wood Council (CWC) began specifically investigating encapsulation techniques during their Mid-Rise Wood Buildings Consortium research project, and demonstrated that direct applied gypsum board, cement board and gypsum-concrete can delay the effects of fire on a wood substrate .
There is extensive data on the use of gypsum board as a means of encapsulation for wood-frame assemblies and cold-formed steel assemblies. However, tall wood buildings are more likely to employ mass timber elements due to higher load conditions, requirements for longer fire resistance ratings, as well as other factors. There is little knowledge currently available related to using gypsum board directly applied to mass timber, or in other configurations, for fire protection. Testing performed to date has been limited to direct applied Type X gypsum board using standard screw spacing, and showed promising results [5, 6, 7]. This represents an opportunity for other configurations that might provide enhanced protection of wood elements to be investigated.
Being able to provide equivalent fire performance of assemblies between non-combustible and combustible construction will thus improve the competiveness of tall timber buildings by providing additional options for designers.
These tests were performed to support the approval and construction of a tall wood building in Quebec City (13-storey). While a calculation methodology is provided in Chapter 8 (Fire) of the CLT Handbook , the Association des Chefs en Sécurité Incendie du Québec (ACSIQ), the Régie du bâtiment du Québec (RBQ) and other stakeholders requested these tests be performed so that they could witness the actual fire performance of the specified assemblies. As such, the main objective was to demonstrate at least a 2 h FRR of the CLT assemblies, which is the minimum required rating as prescribed by the National Building Code of Canada  for structural elements and fire separation walls of exit stair ways and elevators shafts in tall buildings (greater than 6 storeys).
Numerous representatives from Quebec and Ontario were present for either one or both days of testing, including RBQ, the Cities of Montreal, Ottawa, and Quebec City as well as fire services personnel from Montreal, Ottawa and Gatineau. FPInnovations, Nordic, the Canadian Wood Council (CWC), and CHM fire consultants were also in attendance.
Building regulations require that key building assemblies exhibit sufficient fire-resistance to allow time for occupants to escape and to minimize property losses. The intent is to compartmentalize the structure to prevent the spread of fire and smoke, and to ensure structural adequacy to prevent or delay collapse. The fire-resistance rating of a building assembly has traditionally been assessed by subjecting a replicate of the assembly to the standard fire-resistance test, (ULC S101 in Canada, ASTM E119 in the USA and ISO 834 in most other countries).
Massive wood elements such as solid sawn timbers, glued laminated timber (glulam) and structural composite lumber (SCL) can provide excellent fire-resistance. This is due to the inherent nature of thick timber members to char slowly when exposed to fire allowing massive wood systems to maintain significant structural resistance for extended durations when exposed to fire. Calculating the fire-resistance of massive wood elements can be relatively simple because of the essentially constant and predictable rate of charring during the standard fire exposure. Charred wood is assumed to no longer provide any strength and stiffness; therefore the remaining (or reduced) cross-section must be capable of carrying the load.
This report presents two (2) mechanics-based design procedures as alternative design methods to conducting fire-resistance tests in compliance with ULC S101 or to using Appendix D-2.11 of the NBCC, which is limited to glulam members stressed in bending or axial compression. The procedures are applicable to solid sawn timber, glulam or SCL structural members and aim at developing a suitable calculation method that would provide accurate fire-resistance predictions when compared to test data. The long-term objective is to provide recommendations for incorporating either method into CSA O86 and/or NBCC.
The comparisons between the proposed methodologies and the experimental data for beams, columns and tension members show good agreement. While further refinement of these methods is possible, these comparisons suggest that the use of the CSA O86 equations and a load combination for rare events adequately address fire-resistance design of massive wood members.
There is a need to evaluate TCC systems under fire conditions to understand how shear connectors will perform and might affect the fire performance and the composite action of the assembly. This project evaluates the fire performance of TCC assemblies based on their structural resistance, integrity and insulation when exposed to a standard fire, as well as how mass timber and concrete interact. This study involves full-scale fire resistance tests on composite wood-concrete floors using two types of shear connectors. 301009649
A series of 3 cross-laminated timber (CLT) fire-resistance tests were conducted in accordance with ULC S101 standard as required in the National Building Code of Canada.
The first two tests were 3-ply wall assemblies which were 105 mm thick, one unprotected and the other protected with an intumescent coating, FLAMEBLOC® GS 200, on the exposed surface. The walls were loaded to 295 kN/m (20 250 lb./ft.). The unprotected assembly failed structurally after 32 minutes, and the protected assembly failed after 25 minutes.
The third test consisted of a 175 mm thick 5-ply CLT floor assembly which used wood I-joists, resilient channels, insulation and 15.9 mm ( in.) Type X gypsum board protection. A uniform load of 5.07 kPa (106 lb./ft²) was applied. The floor assembly failed after 138 min due to integrity.
The overall objective of this research is to develop a methodology that will foster the design of fire-safe buildings of wood or hybrid construction. This project aims to develop a design methodology (i.e., calculation methods) which will allow the calculation of the fire-resistance of CLT assemblies/construction. The methodology will take into account the thickness and number of laminations and their orientation, the species and strength properties of the laminations, the load imposed on the panel, and any additional fire protection such as gypsum board or plywood. This will provide manufacturers and designers a methodology to predict the fire-resistance of panels for use in various applications.
In order to establish calculation methods a series of experimental tests has been undertaken. To date, two CLT fire-resistance tests have been conducted at the NRC fire laboratory where the panels were subject to standard CAN/ULC-S101 fire exposure. Both 3-ply CLT assemblies consisted of 38 x 89 mm black spruce boards, where the two outer longitudinal plies consisted of SPF 1650Fb-1.5E machine stress-rated (MSR) lumber, and the inner transverse ply was SPF No.3/stud. Each panel was protected with two layers of 12.7 mm CGC Sheetrock® FireCode® Core Type X gypsum board. Thermocouples were placed behind each layer of gypsum board and embedded at 19-mm increments into the panels to a depth of 76 mm.
The first test was a floor assembly, where a load of 2.7 kPa was applied. The test was ended after 77 minutes due to equipment concerns from the laboratory staff, therefore structural failure was not reached. The greatest measured char depth in the panel was 11.2 mm. The maximum deflection of the floor was 32.1 mm.
The second test was a wall assembly, which failed due to buckling after 106 minutes when subjected to 333 kN/m. From one data point a charring rate of 0.4 mm/min was calculated. The maximum deflection of the wall was 55.3 mm. From the thermocouple data, it was determined that the two layers of gypsum delayed the onset of charring in both the floor and wall tests by approximately 60 minutes.
So far the proposed calculation methods have proved to be conservative in predicting the time to structural failure and charring rates.
Due to the difficulty of sourcing CLT assemblies to test, six additional full-scale fire resistance tests are to be completed in 2011-2012. The current test plan includes testing two more wall assemblies and four more floor assemblies. Tentatively, the next set of floor tests to be completed will be on a 5 ply unprotected assembly with the only difference between them being the type of adhesive used. Similarly, a 5-ply unprotected wall assembly will be tested. A composite floor assembly consisting of CLT with a concrete toping is also planned to be tested. This leaves one wall and one floor test to be finalized allowing for investigation of any questions raised in the tests identified above.
This study was part of a broader project entitled Glulam and CLT Innovative Manufacturing Process and Product Development. The main objective of the current study is to evaluate the effect of CLT panels manufacturing parameters on its fire resistance. More specifically:
§ To evaluate the effect of CLT manufacturing (gluing) parameters on the heat delamination resistance under standard fire conditions;
§ To improve the fire-resistance of the CLT panels.
The objective of the study is to identify current and available solutions for improving the fire resistance of wood I-joists. After an analysis and comparison of these technologies, the most promising solutions will be presented which will be suggested to wood I-joist manufacturers for potential further investigation.
Fire Resistant - Joints
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FPInnovations is involved in a large research project regarding CLT construction. One objective of this research is the creation of a design methodology for calculating the fire-resistance of CLT assemblies/construction. This methodology will foster the design of fire-safe buildings of wood or hybrid construction. In order to establish such calculation methods, a series of experimental tests has been undertaken. A total of eight full-scale CLT fire resistance tests have been conducted at the NRC fire laboratory where the panels were subject to the standard ULC S101  fire exposure. The series consisted of three wall and five floor tests. Each test was unique using panels with a different number of plies and varying thicknesses. Some of the assemblies were protected using CGC Sheetrock® FireCode® Core Type X gypsum board while others were left unprotected.
The panels were instrumented with thermocouples and deflections gauges. Thermocouples were placed in accordance with the standard layout. In addition, thermocouples were placed in between the CLT plies and at mid-depth of each ply at five locations. In tests where the panels were protected, thermocouples were also placed between the layers of gypsum board as well as between the gypsum board and the panels.
Test 1 was a 3-ply floor assembly protected with two layers of ½” Type X gypsum board. A load of 2.7 kPa was applied. The test was terminated at 77 minutes due to equipment concerns from the laboratory staff; therefore structural failure was not reached. The maximum deflection of the floor was 32.1 mm.
Test 2 was a 3-ply wall assembly protected with two layers of ½” Type X gypsum board, which failed structurally due to buckling after 106 minutes when subjected to a load of 333 kN/m. From one data point a charring rate of 0.4 mm/min was calculated. The maximum average deflection of the wall was 47.5 mm. The two layers of gypsum delayed the onset of charring in both the floor and wall tests by approximately 60 minutes.
Test 3 was an unprotected 5-ply floor with an applied load of 11.75 kPa. The floor failed after 96 minutes when flames were observed at one of the joints. The maximum deflection was 129.4 mm.
Test 4 was an unprotected 5-ply wall with an applied load of 333 kN/m. The wall failed after 113 minutes due to structural failure. The assembly popped out of the furnace possibly to a loading eccentricity that developed as the panels charred during the test. The maximum deflection was 47.7 mm.
Test 5 was a 3-ply floor protected with one layer of 5/8” Type X gypsum board. A load of 2.4 kPa was applied. The floor failed after 86 minutes due to flames observed at one of the joints. The maximum deflection was 321.4 mm.
Test 6 was a 5-ply floor protected with one layer of 5/8” Type X gypsum board. A load of 8.1 kPa was applied. The floor failed after 124 minutes due to flames observed at one of the joints. The maximum deflection was 153 mm.
Test 7 was an unprotected 7-ply floor. A load of 14.58 kPa was applied. The floor failed after 178 minutes due to structural failure. The maximum deflection was 170 mm.
Test 8 was a 5-ply wall with 21 mm plies. A load of 72 kN/m was applied. The wall failed after 57 minutes due to structural failure. The maximum deflection was 77 mm.